Category Archives: DOSBox

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No really, it’s Catacomb 3-D: The Descent. First ported to 32-bit SDL by NotStiller. Me being the person I am, I fixed a slight bug regarding binary files on Windows, and MS-DOS, then cleaned up some of the C++ syntax (yuck!) making it far more C89 friendly. And of course, hot off the heels of DooM for GO32 DPMI, I was able to get it to build and run using GCC 1.39 and GO32.

I know most people really won’t care, but I found it kind of interesting. I should try to see if it’ll run on actual hardware, just as a comparison of tightly optimized Borland C++ / Assembly vs 100% pure C on DJGPP. The best tech of 1991 for sure!

So I wanted to install Borland C++ 3.1 under DOSBox to compile something ancient. I’m on a MAC so MS-DOS player is not currently an option. I have disk images, which p7zip can happily break down into files, giving me a bunch of files in a single directory, the perfect thing to mount as a ‘disk’ under DOSBox. However I had subdirectories with patches, source and other stuff in my virtual ‘floppy disk’. And the installer bombed. Turns out it wasn’t any file limitation, or anything in the guest C: drive, no the Borland installer doesn’t like sub directories on the install source.

Remove those, and it’ll install just fine.

Also, maybe it’s the weird Borland extender, but Borland C 2.0 runs WAY faster under DOSBox than version 3.1

Around the time of the x68000 port of DooM, I was cutting down the DooM source for a null/portable version. I never could get it to actually run either using EMX or DJGPP 1.03, as I couldn’t get it to link to save my life with a constant never ending battle of unresolved symbols. After a while I just used what I had towards the x68000 version and concentrated on getting it up and running, and just shelved the null/portable effort.

Later on I wanted to get it running again as part of messing with another cross compiler, as DooM isn’t a trivial application to port and verify correct operation. And in the process of trying to get the null version to build and run on Windows using TDM GCC, I wanted to make sure it at least kept compiling with GCC v1.x.

Once more again I was able to compile individual files but unable to link. But this time, I just looked at the diffs for binutils, I thought it should be somewhat easy to get hosted on Windows. Although versions may point to binutils 1.0, I had to use binutils-1.9.tar.gz even though the diffs are against Mar 24 1991, and the source for 1.9 is dated April 17 1991.

My first effort gave me a linker that would happily link, but go32 would either refuse to run the executable, or just crash. I was going to give up again, but I found mention in another file that DJGPP actually uses the linker from G++, the C++ compiler which was a separate thing in the late ’80s and early’90’s. This time it worked, and I could link a trivial hello world style application!

Now that I finally had a cross linker actually working, I didn’t want to compile under emulation, so looking at the other diffs, they didn’t look too extensive. I went ahead ,and took DJGPP v1.06 and patched up the compiler & assembler to get a full cross toolchain. And in no time, I had a null version of DooM running on MS-DOS well at least tested on DOSBox.

This was fun, and all but I didn’t see any easy way to do fun things like hook interrupts so I could get the keyboard & clock like any good MS-DOS program. DPMI greatly eased this kind of stuff, so looking at the DJGPP history, DJGPP v1 version 1.10 actually adds preliminary DPMI support! And in the next version, DPMI was much more better supported, however the binary format had changed from a.out to COFF as part of the move to v1.11. I was able to take the memory, and DPMI portions from the final v1.12 libc, and manually build and run them against the v1.06 library / dev tools.

And much to my surprise, it actually worked! At least having the wrong format didn’t have any effect on how GO32 worked for me.

So feeling lazy, I snagged some of the support code from Maraakate’s revamp of DooM, just to make sure of the timer code, and the keyboard code, and again verified that I can build with the keyboard & timer ISR and I’m able to play the v1.9 shareware & commercial levels fine. I haven’t done a thing to clean up or update the DooM source itself against all the dozens of bugs and issues with Ultimate DooM, or other games like Chex Quest etc.

Although I’m using DPMI to drive realtime events, if I looked further at the GO32 v1.06 environments I could either figure out how it operates it’s timer, or modify the extender directly to drive the PIC timer and keyboard as I need. But overlooking that, the vintage 1991 software is more than capable of running DooM.

Long story short, Wayne was able to exploit a ‘feature’ of older non random address location where a machine is configured the same way will always load the same program in the same address space. Using this knowledge he was able to work out in memory where the location of the plane was kept in memory. Adding a ‘server’ and two ‘client’ versions of DOSBox he could then transmit the location of the plane to the two other DOSBox client’s and then just set their viewports to left & right, and now he has an immersive simulation.

As you can see it clearly can see the USB device, but when it opens the device it fails. And yes I’ve tried Administrator. And for the hell of it, I fire up Windows XP on VMWare, connect the USB dongal, and amazingly:

So, how to use the thing? Well in Windows Vista onward (8/8.1/10..) Microsoft decided to hide the MIDI selection tools, making this a mission to see what mapper you are using. But using DOSBox it’s easy to see which is which. In DOSBox run:

While I was looking for System16 stuff, I found the first version of MAME to include the UAE 68000 core starting in release MAME 28, although System16 emulation itself didn’t appear until MAME 33b3, but not playable until MAME 33b4.

So what does it mean? Well at the time the UAE core was the way to go. However from looking at the MAME source, the UAE core that they were using from System16 was already generated, while UAE still included the build68k program to parse the tables, and generate the 68000. Instead they were editing the outputted C. UAE wasn’t GPL until version 0.7(something), 0.7.6 for sure, so I don’t know why they weren’t using it from the source.

Eventually starting in MAME 35b2, the core was replaced with MUSASHI , so Among their reasons for dumping the early UAE CPU core was this laundry list:

New 68000 C core. For testing purposes, this is also being used in the DOS
version instead of the asm core. [Karl Stenerud]
Differences:

1. Faster. This code is, barring ram fetch time, almost twice as fast as the
existing C core in MAME. I’ve done extensive speed profiling on both
engines. The only problem now is the slow memory access in MAME due to
bankswitching et al.

2. Emulation more correct. I found many bugs in the MAME engine (and many,
many more in mine for that matter) when I pitted them head-to-head.
I have run random instructions from each opcode class at least 10 million
times, comparing the resultant CPU states, and have left it running random
instructions for 1 billion iterations. In every case, I have adhered to
the specs defined in M68000PM/AD REV. 1.

3. Disassembler is correct. The current M68000 disassembler in mame has a
tendency to disassemble instructions that have an invalid EA mode.

4. Cycle counting is 99.9% correct. The only instructions which don’t have
correct cycle counts are divs, divu, muls, mulu, and they’re not worth
counting correctly. (I’m not about to waste emulation time counting 0-1 and
1-0 sequences).

5. > 32 bit friendly. I’ve taken care to ensure maximum portability without
sacrificing speed. The result is conditional compiling dependant on your
architecture. I’ve also implemented and tested a compatible solution for
architectures that lack 8, 16, or 32 bit signed storage types.

6. The code is carefully laid out to be readable.

Also in MAME 35b4 added in was emulation of the NEC uPD7759 chip for speech, fleshing out the System16 emulation.

To compile these ancient versions, and inbetween I was using my Candadian cross DJGPP GCC 4.12 Win32 cross compiler. For Allegro I’ve always found it builds far easier using GCC 2.7.2.1, a vintage compiler from back in the day I could just run in DOSBox.

Alien Syndrome

Obviously with today’s machines, these ancient versions of MAME run fine on DOSBox! It’s really amazing in the scope of emulators running emulators.

From wikipedia:
The casino computer virus is a malicious virus that upon running the infected file, copies the File Allocation Tables (FATs) to random-access memory (RAM), then deletes the FAT from the hard disk. It challenges the user to a game of Jackpot of which they have 5 credits to play with, hence the name. No matter if they win or lose, the computer shuts down, thereby making them have to reinstall their DOS.

So with all the excitement with jsDOSBox it was about time I tried to get something from my old java dosbox stuff running again.

As a quick note, as of right now, you cannot boot into a disk image… Nor can you really run bat files, or any kind of drivers beforehand. It’s basically either use a script that adds files one by one, or use an image file which gets mounted, and you run your exe/com file from that.

So here we go, back again is the old Fortran Dungeon (zork) compiled with QuickC for Windows, running on the working model version of Windows 3.0.